US9108524B2ActiveUtilityPatentIndex 84
Battery SOC estimation with automatic correction
Assignee: GM GLOBAL TECH OPERATIONS INCPriority: Oct 22, 2013Filed: Oct 22, 2013Granted: Aug 18, 2015
Est. expiryOct 22, 2033(~7.3 yrs left)· nominal 20-yr term from priority
B60L 58/12B60W 20/00B60L 11/1861Y02T10/70B60L 2250/16B60L 2240/545G01R 31/382G01R 31/3828B60L 2240/547B60L 2240/549G01R 31/3835G01R 31/3648
84
PatentIndex Score
12
Cited by
14
References
18
Claims
Abstract
An embodiment contemplates a method of determining a state-of-charge of a battery for a vehicle. (a) An OCV is measured for a current vehicle ignition startup after ignition off for at least eight hours. (b) An SOC OCV is determined for the current vehicle ignition startup. (c) An SOC OCV — est is determined for a current vehicle ignition startup. (d) A determination is made whether the difference in the SOC OCV for the current startup and the SOC OCV est for the current startup is less than a predefined error bound using. Steps (a)-(d) is performed in response to the difference being greater than the predefined error; otherwise, determining an ignition-off current for the current vehicle ignition startup as a function of the SOC OCV of the current vehicle ignition startup and previous vehicle ignition startup, and a SOC based on current integration over time. Determining an SOC est of the current vehicle ignition startup using the processor.
Claims
exact text as granted — not AI-modifiedWhat is claimed is:
1. A method of determining a state-of-charge of a battery for a vehicle, the vehicle being in a charging state when the engine is operating and a non-charging state when the engine is not operating, the method comprising the steps of:
(a) measuring an open circuit voltage (OCV) for a current vehicle ignition startup using a voltmeter, wherein the current vehicle ignition start-up is performed after the vehicle is in the non-charging state for at least eight hours;
(b) determining an open circuit voltage-based state of charge (SOC OCV ) for the current vehicle ignition startup using the processor;
(c) determining an estimated open circuit-based state of charge (SOC OCV — est ) for a current vehicle ignition startup using the processor;
(d) determining whether the difference in the SOC OCV for the current vehicle ignition startup and the SOC OCV est for the current vehicle ignition startup is less than a predefined error bound using the processor;
(e) performing steps (a)-(d) in response to the difference being greater than the predefined error; otherwise, proceeding to step (f);
(f) determining an ignition-off current for the current vehicle ignition startup as a function of the SOC OCV of the current vehicle ignition startup, an SOC OCV of a previous vehicle ignition startup, and a state-of-charge based on current integration over time using the processor technique;
(g) determining an estimated state of charge (SOC est ) of the current vehicle ignition startup using the processor; and
(h) providing the SOC est to a vehicle subsystem for use in a vehicle operation where the battery state-of-charge is utilized.
2. The method of claim 1 wherein estimating a SOC est of the current vehicle ignition startup is determined as a function of the SOC est of a previous vehicle ignition startup, a state-of-charge based on an ignition-on current integration over time, and a state-of-charge based on the ignition-off current integration over time.
3. The method of claim 2 wherein estimating a SOC est of the current vehicle ignition startup is represented by the following formula:
SOC
(
est
)
(
k
)
=
SOC
est
(
k
-
1
)
+
1
C
norm
∫
ρ
·
I
on
(
k
-
1
)
·
ⅆ
t
+
1
C
norm
I
off
(
k
-
1
)
·
Δ
t
off
(
k
-
1
)
where SOC est (k−1) is the estimated state-of-charge at the k−1 ignition start, C norm is the battery capacity, ρ is the charge efficiency, I on is the ignition on-current of the previous vehicle ignition start, I off is the ignition on-current of the previous vehicle ignition start, and Δt is the time.
4. The method of claim 1 wherein the SOC OCV — est for a current vehicle ignition startup is determined by the following formula:
SOC OCV — est ( k )=SOC OCV ( k−i )+ΔSOC
where SOC OCV (k−i) is and open circuit voltage based SOC at ignition k−i, and ΔSOC is the integration of ignition-on current from ignition k−i to ignition k, and i is a count of the vehicle ignition startup.
5. The method of claim 1 wherein if no error is present in the measurement data, then the formula for determining the vehicle ignition-off current is determined as follows:
I
off
(
k
)
=
[
SOC
(
k
)
-
SOC
(
k
-
1
)
-
1
C
norm
∫
ρ
·
I
on
(
k
-
1
,
t
)
·
ⅆ
t
]
·
C
norm
/
Δ
t
off
(
k
-
1
)
where SOC(k) is the state-of-charge at the k th ignition start, SOC(k−1) is the state-of-charge at the k−1 ignition start, I on is the ignition-on current, I off is the ignition-off current, ρ is the charge efficiency, and t is the time.
6. The method of claim 1 wherein if measurement data error is present and an error distribution is non-uniform, then a particle filter is used for determining the ignition-off current.
7. The method of claim 6 wherein a state space model is defined and a measurement model is defined for determining the ignition-off current.
8. The method of claim 7 wherein the state space model of the SOC for current vehicle ignition startup is defined by the following formula:
SOC
(
k
)
=
SOC
(
k
-
1
)
+
1
C
norm
∫
ρ
·
I
on
·
ⅆ
t
+
1
C
norm
I
off
·
Δ
t
off
+
ɛ
SOC
where SOC(k) is the state-of-charge at the k th ignition start, SOC(k−1) is the state-of-charge at the k−1 ignition start, C norm is the battery, I on is the ignition-on current, I off is the ignition-off current, ρ is the charge efficiency, Δt is the time, and ε SOC is an error the measurement data of a current sensor in the SOC determination.
9. The method of claim 8 wherein the state space model of the ignition-off current for the vehicle ignition startup is defined by the following formula:
I off ( k )= I off ( k− 1)+ε 1
where I off (k) is the ignition-off current for the current vehicle startup, and I off (k−1) is the ignition-off current for the previous vehicle startup, and ε 1 is the measurement error of a current sensor.
10. The method of claim 7 wherein the measurement model is defined by the following formula:
SOC off ( k )=SOC OCV ( k )−ε OCV
where SOC off (k) is the ignition-off current for the current vehicle startup, and SOC OCV (k−1) is the ignition-off current for the previous vehicle startup, and ε OCV is the measurement error of the current sensor for the OCV.
11. The method of claim 7 wherein determining the ignition-off current using the particle filter comprises the following steps of:
initializing a particle set;
updating a respective particle in the particle set based on the state space model for determining a estimate of the SOC est at a k th ignition start using the state space model;
calculate a weighting factor that is a function of the SOC at a k th ignition start and the estimate SOC est at a k th ignition start;
resampling a particle set as a function of the weighting factor; and
estimating the weighted average of the ignition-off current at current ignition startup.
12. The method of claim 11 wherein the particle set of I off i (0) for i=1, 2, . . . , N.
13. The method of claim 12 wherein the weighting factor is represented by the following formula:
w
i
(
k
)
=
1
σ
2
π
ⅇ
-
[
SO
C
^
l
(
k
)
-
SOC
(
k
)
]
2
/
2
σ
2
where σ is the standard deviation of the SOC est .
14. The method of claim 13 wherein the estimated weighted average of the ignition-off current is represented by the following formula:
I off ( k )=Σ i w i ( k ) I off i ( k )
where w i (k) is a respective weight for a particle at each respective ignition start, and I off i (k) is the measured ignition off current for each particle at each respective ignition start.
15. The method of claim 1 wherein if current sensor error is determined and an error distribution is uniform, then a Kalman filter is used for determining the ignition-off current.
16. The method of claim 1 wherein the step of providing the SOC est to a vehicle subsystem for use in a vehicle operation includes outputting the SOC est to a display device for identifying the state-of-charge to the operator of the vehicle.
17. The method of claim 1 further comprising the step of determining whether the estimated SOC is utilized for a duration of time greater than a predetermined period of time, and wherein a return is made to step (a) if the estimated SOC being utilized for a duration of time that is greater than the predetermined period of time.
18. The method of claim 17 wherein if the estimated SOC is utilized for a duration of time that is less than a predetermined period of time, the method comprises the following steps:
determining whether the current ignition-off time is greater than eight hours and the SOC OCV is within an error bound; and
proceeding to step (f) in response to determining that the current ignition-off time is greater than eight hours and the SOC OCV is within the error bound, otherwise proceeding to step (a).Cited by (0)
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